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Old 15th August 2004, 08:39 PM   #1
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Default bridge a 4 ch amp into 3 ch?

Hey, new here, just have a question:

I was wondering if it would be possible to bridge, say, a 4 channel amp in a fashion that would leave 2 of the channels isolated (for 2 6x9 speakers) and combine the remaining 2 to power a single woofer (this would result in 3 channels.) Can this be done? Or are you only able to bridge it into a 2 channel or single channel amp?

Thanks in advance,

Jared
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Old 16th August 2004, 01:27 AM   #2
clayton is offline clayton  United States
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Yes you can. What kind of amp is it? Do you have the owners manual for it? If not maybe we can help you out.
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Old 16th August 2004, 01:35 AM   #3
getafix is offline getafix  Philippines
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I agree with clayton, but why power your rear speakers? might as well use that for your front? or do you already have a seperate amp for your front speakers?
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Old 16th August 2004, 02:49 AM   #4
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thanks for the reply!

well, i haven't actually bought an amp yet...

in my current setup (everything aftermarket) i have a nice kenwood reciever (25 amps rms) powering some pioneers: 2 front 5 1/4's and 2 rear 6x9's

My 6x9's are fairly efficient, and they sound very good, but now i've decided that it would be a good thing to give them a little more power. I'd also like to add a sub to the system. What i'm aiming for is have just my front 5 1/4's powered by the reciever and 6x9's and a sub powered by an external amp.

I was just making sure that i could do this with a single amp, or if this is the best method..
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Old 16th August 2004, 07:06 AM   #5
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I've done that kind of thing before, when I was young and foolish.

A few things to mention:

1. There are several decent 5 channel amps on the market at reasonable prices.

2. If you're going to amplify only one pair of channels, you really ought to consider making them the fronts. The front channels are far more important to overall sound quality than the rears.

3. If you cannot afford to buy amps for all of the channels, you may still be better off leaving all of the main speakers on deck power, and spending a bit more on the sub amp. Buy something that you shouldn't need to replace. (I've spent more money than I care to consider on stuff that I replaced later, and knew that I would when I bought it.) I really wish that I'd gone in stages and bought better stuff the first time out, instead of buying a whole system on a limited budget.

Best of luck.
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Old 16th August 2004, 08:08 AM   #6
Jennice is offline Jennice  Denmark
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In theory, no problem.
In reality, make dure that your amp is stable in bridge mode with the speaker impedance you're going to use. (4 ohm or whatever your choosen driver is).

Also, don't go by "peak" or "music" power ratings. Equipment manufacturers are - in my oppinion - very eager to specify power ratings that are impossible or useless theoretical values.

Regarding which speakers to power seperately, my idea would be to power those that are the hardest to drive. Some head units actually sound decent, as long as the speakers aren't too hard to drive. A suggestion could be to buy a good, less-than-five channel amplifier now, and buy amplification for the rest later on, when budget permits. Rather have a few channels of high quality amplified, than 5 channels in poor quality.

Jennice
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Old 16th August 2004, 02:33 PM   #7
getafix is offline getafix  Philippines
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Quote:
Originally posted by batonrye
thanks for the reply!

well, i haven't actually bought an amp yet...

in my current setup (everything aftermarket) i have a nice kenwood reciever (25 amps rms) powering some pioneers: 2 front 5 1/4's and 2 rear 6x9's

My 6x9's are fairly efficient, and they sound very good, but now i've decided that it would be a good thing to give them a little more power. I'd also like to add a sub to the system. What i'm aiming for is have just my front 5 1/4's powered by the reciever and 6x9's and a sub powered by an external amp.

I was just making sure that i could do this with a single amp, or if this is the best method..
I strongly suggest that you power your fronts with the amps and use the receiver for the 6x9 at the rear. As like SupraGuy said, the fronts are infinitely more important than the rear speakers.

at the moment you seem to have a good plan.
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Old 17th August 2004, 02:01 AM   #8
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Ok, after considering all of your responses I have deviated a bit from my original plan...

I would now like to amplify both my rear and front, and I would also like to add a sub on a separate amp to fill in more of the bass.

My new question is this: Since i cannot afford to do both at the moment, and do it right, which purchase to you think would benefit my system the most? Buy a 4-ch amp for my front and rear (take in mind that my current amp is *decent*) or add a sub w/ separate amp to the system? On the subject, would a single sub suffice or would a pair be more ideal?

Thanks again,

Jared
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Old 17th August 2004, 10:37 PM   #9
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Personally, I think that a good sub will add a lot more noticable improvement in a system. It may need to be turned down to match with existing amps, but if you do it right, no problem.

For the single/dual question, that's going to depend on a number of factors:

How much space are you willing to give up for the subs? More and larger subs will take more space.

How much bass are you really going to want? If you're just looking for a bit of low end on some good old rock and roll, then a single 10" will probably do the trick.

If you want more low bass, for dance/rap/techno music, something that'll rumble okay, then you may want to look into a 12" But as long as you're not looking to set off car alarms for a block radius, just one should do.

I've got a pair of 10" in my car, although when one of them got damaged (loose box in the hatch hit the cone) I was using just a single for a while, and had I heard that before I bought the second one, I probably would have left it at that. The second one does allow me to go a bit deeper, and makes it a couple dB louder, but for my listening habbits, it wasn't really needed.

What will be of more importance to you is what kind of enclosure you want to put the sub(s) in.

A sealed enclosure is small, easy to build, and les critical of tolerances. It tends to provide lots of "tight" bass, and exhibits better overall power handling at extended low frequencies. Also, because of the shallow low end rolloff of a sealed enclosure, extremely low frequencies are actually easier to produce in a sealed enclosure than they are in other kinds. This is what I'm using, due to the low space requirements.

A ported enclosure is a bit more complex, will be a bit larger, but it is more efficient at low frequencies down to the port frequency, below which it will drop off at twice the rate of a sealed box. Power handling below port frequency is also poor, but overall, this is an excellent choice A ported enclosure produces the least distortion of any enclosure type, making it a popular choice for audiophile listening requirements.

A bandpass box is very efficient within the bandpass frequencies, with sharp cutoffs above and bleow the pass-band. These are often capable of producing as much as 8dB greater SPL than an equivalent sealed or ported enclosure. (That's the rough equivalent of 5 or 6 times the amplifier power!) They tend to carry greater distortion, and are much harder to "blend" into the rest of the system speakers. (Not to say it can't be done, but it's HARD.) They will also take up more of your trunk space. It is possible for a woofer to be in serious trouble in a bandpass box, but because of the extreme cone control, you won't hear it until way too late.

The enclosure is at least as important as the speaker that you put in it, and in some cases, it's more important. A cheap woofer in a box which is well designed and suited to the woofer will sound far better than an excellent woofer in a cheap box. Keep this in mind when you are budgeting for your install. If you build the box yourself, make sure that you check and double check that it will work.
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